1. Field of the Invention
The present invention relates to a CMOS (complementary metal-oxide-semiconductor) image sensor and a manufacturing method thereof, and more particularly, to a CMOS image sensor substantially un-damaged by etching of a photodiode region, and to a manufacturing method thereof.
2. Description of Related Art
A CMOS image sensor is an image capturing device having low power consumption and small size. The CMOS image sensor is widely used in digital cameras and mobile phones. It is technologically important to reduce a dark current in the CMOS image sensor. The dark current can result in deteriorating image quality and the occurrence of white points when charges caused by the dark current are greater than charges corresponding to light received by a photodiode of the CMOS.
The dark current may be caused by many factors. Specifically, dangling bonds exiting on a photodiode surface of a silicon substrate contribute to the generation of the dark current. The dangling bonds on the surface of the silicon substrate are generated by unstable polymerization and are affected by surface damage from dry etching during the process of manufacturing the CMOS image sensor. For example, when an upper surface of the photodiode is damaged by plasma dry etching during the manufacturing process, the polymerization on the surface becomes unstable and the dark current results during operation of the CMOS.